To provide cellular wireless communication service, a wireless service provider typically operates an access network that functions to connect one or more access terminals (e.g., cell phones, PDAs, laptops, netbooks, tablets, and/or other wirelessly-equipped devices) with one or more transport networks. In a typical access network, an area is divided geographically into a number of coverage areas, such as cells and sectors, each defined by a radio frequency (RF) radiation pattern from a respective base transceiver station (BTS). Within each coverage area, the BTS's RF radiation pattern may provide one or more wireless links, each on a carrier (or set of carriers), over which access terminals may communicate with the access network. In turn, the access network may provide connectivity with the public switched telephone network (PSTN), the Internet, and/or other transport networks.
The wireless links may carry communications between the access network and the access terminals according to any of a variety of wireless protocols. Depending on the protocol employed, each wireless link may also be divided into a plurality of channels for carrying communications between the access network and the access terminals. For example, each wireless link may include a plurality of forward-link channels, such as forward traffic channels, for carrying communications from the access network to the access terminals. As another example, each wireless link may include a plurality of reverse-link channels, such as reverse traffic channels, for carrying communications from the access terminals to the access network. In many wireless protocols, the access network and active access terminals may engage in a power-control process to control transmission power for communications over established traffic channels. For purposes of illustration, the embodiments herein will be described by way of example with reference to a power-control process carried out by the access network to control the reverse transmission power of the active access terminals. It should be understood, however, that a similar power-control process may be carried out by the active access terminals to control the forward transmission power of the access network.
In an example power-control process, an access network may regularly send power control commands (PCCs) directed to the active access terminal, to control the active access terminal's transmission power on a reverse traffic channel with the access network (i.e., the reverse transmission power). For example, the access network may regularly compare a signal-quality metric of reverse traffic-channel communications received from the active access terminal to a signal-quality threshold value and thereby decide whether to send a “power up” PCC that instructs the active access terminal to increase its reverse transmission power or a “power down” PCC that instructs the active access terminal to decrease its reverse transmission power. For instance, if the signal-quality metric is less than the signal-quality threshold value (thus indicating a weaker signal), the access network may send a “power up” PCC directed to the active access terminal. Alternatively, if the signal-quality metric is greater than the signal-quality threshold value (thus indicating a stronger signal), the access network may send a “power down” PCC directed to the active access terminal.
As a result of the access network regularly sending PCCs directed to the active access terminal, the active access terminal may regularly receive PCCs from the access network. (It should be understood, however, that the active access terminal may fail to receive some PCCs sent by the access network due to poor forward-link conditions or other factors.) In response to each PCC received from the access network, the active access terminal may then responsively adjust its reverse transmission power in accordance with the PCC. For instance, in response to receiving a “power up” PCC from the access network, the active access terminal may increase its reverse transmission power. And in response to receiving a “power down” PCC from the access network, the active access terminal may decrease its reverse transmission power.
Advantageously, this power-control process may enable the active access terminal and the access network to balance between keeping traffic-channel communications strong enough to overcome interference and preventing traffic-channel communications from becoming so strong that they unduly interfere with other communications.